A Mr. I (originally parsed Mr. I.[1]) is an enemy species in the Mario franchise. Its name is self-descriptive; they seem to be nothing more than a giant eyeball. Additionally, Mr. I are usually completely immobile, as they can only rotate around in place.

They first appear in Super Mario 64, where the only thing they can do is shoot pink bubbles at Mario from their pupils. They always watch Mario when he is close, and can be dizzied into submission if Mario runs in a circle around them in either direction, rewarding Mario with a Blue Coin. The much larger version, Big Mr. I, is in the attic of Big Boo's Haunt. The standard Mr. I can be found in Big Boo's Haunt, Lethal Lava Land, and the Hazy Maze Cave.

In the remake, their pupils are now oval-shaped, and said pupils are now dark blue instead of black. Also, the bubbles were changed to balls of light that change color, but are primarily turquoise.

Big Mr. I appears in Mario Party 2 in the Horror Land board, where he offers to "warp" the player across the board for ten coins, though his "warping" actually involves him rolling and chasing the player (and any others along the route) to the other side of the board.

In Mario Party 8, Mr. I and Big Mr. I appear in the minigame Eyebrawl, where instead of running around them like in the Eye Sore minigame, the player must draw circles around them with the Wii Remote. In this game, Mr. I take on a more oblong shape. Whoever gets Mr. I dizzy first wins the minigame. The loser is haunted by Mr. I.

It's a Mister I. These bizarre foes can't help but give you the evil eye... Max HP is ??. Attack is 2. It will shoot sharp glances at any enemy it spots... None of your attacks will work... Try flipping and spinning around and around it...

In Super Paper Mario, Mr. I, identified as Mister I, appears in Merlee's Mansion and Castle Bleck; these Mr. I are immune to conventional attacks, and can only be defeated by running around them repeatedly while using Mario's Flip technique. Alternatively, the player may use Fleep's ability on them to defeat much easier. In this appearance, Mr. I attack the player by shooting them with a cyan laser beam. The game also introduces a sub-species of Mr. I called Red I.

In the files for the Super Mario Mash-Up Pack in Minecraft: Wii U Edition, there is a picture of an Ender Chest with a Mr. I on it. The concept for the Mr. I chests was scrapped before the final release, where they are Shy Guy-themed instead.